The invention relates to a conditioning device for biological cells, in particular a conditioning device for conditioning, e.g., manipulation, stimulation, imprinting and/or differentiation of biological cells by an interaction with a conditioning sample. Main applications of the conditioning device consist in the conditioning of biological cells and the examination of their reactions after a contacting by the conditioning sample. Furthermore, the invention relates to conditioning methods that can be realized in particular with the conditioning device.
Biological cells, in particular animal or human cells, are permanently in interaction with adjacent cells, biological surfaces or liquids in the organism. Intermolecular interactions take place between surface molecules of adjacent cells or between surface molecules of a cell with adjacent substances. Molecular surface bondings can be exchanged and molecular signal chains can be induced in the participating cells. The signal chains propagate, e.g., into the cytoplasm, where they influence cell development procedures such as, e.g., the expression of genes (see J. Gerhart in “Theratology”, vol. 60, 1999, pp. 226-239).
For example, a cell differentiation can be initiated or influenced by surface interactions of biological cells. Furthermore, the surface interaction can effect the formation of tissue from biological cells. In pronounced form processes of the signal exchange and of a so-called cellular synchronization can be observed in particular in the cell differentiation or wound healing. Especially the differentiation and multiplication of stem cells is based on the bonding of surface receptors of the stem cells to ligands. During the embryogenesis or a regeneration of tissue (e.g. wound healing) changes of biological cells are induced by surface contacts.
Biologically active molecules, i.e., molecules that induce a change of the biological cell upon contact with the biological cell, in particular the cell surface, are also designated as signal factors. A distinction is made between soluble signal factors that are contained, e.g., in a cultivation medium or a body fluid and surface-bound signal factors that are arranged, e.g., on cell surfaces or on surfaces of aggregates of biological substances or boundary surfaces in the biological organism.
The in vitro examination of the change of biological cells after a contact with the signal factor represents an extremely complex problem for the following reasons. In the first place, every contact of a cell with a molecule in the environment can induce a biologically active interaction. Every contact can represent a piece of molecular information for the cells so that signal chains with changes of cellular states can be initiated. For an examination of the physiologically relevant signal factors false molecular information such as can occur, e.g., by a contact with an artificial surface such as glass, metal or plastic must be avoided by the creation of defined environmental conditions of the cell. However, such artificial surfaces are permanently present in the conventional techniques of cellular biology, e.g., as parts of culture vessels or instruments. In the second place, the in vitro examination becomes complex since a large number of signal factors and signal chains are known that act specifically on cells. In order to test the effect of a certain signal factor or of combinations of signal factors extremely many parameter variations are necessary, e.g., in order to identify one of the 17 signal paths known today of the higher animal cells for which some 10 to some 100 signal factors are active (see above publication of J. Gerhart).
A known concept for the conditioning and in-vitro examinations of biological cells is based on arranging the cells during a test exclusively in a physiological solution or on a surface that is recognized by the cell as physiological surface or at least not as artificial surface. In doing so, a contactless manipulation of the cells takes place, e.g., by dielectrophoretic or optical forces in order to avoid undesired surface contacts.
A generic conditioning method for carrying out this concept is known, e.g., from U.S. Pat. No. 6,991,906 B1. In this technique, which is schematically illustrated in FIG. 9, a first cell 1 is held with a holding device 10′ comprising a group of electrodes for forming a dielectrophoretic field cage 12′. An optical tweezer 20′ is used to hold a second cell 2 and for its movement toward the first cell 1. The second cell 2 forms a sample for the stimulation of the first cell 1. The second cell 2 can be brought in contact with the first cell 1 by the movement of the focus of the optical tweezer 20′. After an interaction an examination of the first cell 1 or a separation of the cells 1, 2 can take place using the optical tweezer 20′.
The technique according to FIG. 9 has a number of disadvantages that limit a practical application for in-vitro examinations. A first disadvantage results from the fact that only individual cell-cell interactions can be examined. For an approach of two cells (or other samples) to the cell 1 two optical tweezers would be required that would, however, mutually disturb one another. Furthermore, the cell 2 can only be moved from certain directions, in particular from above to cell 1, since otherwise the optical tweezer 20′ is shaded by the electrodes 13′ or the cell 1. It can also be disadvantageous that a high light intensity in the focus of the optical tweezer 20′ has an undesired influence on the cells or their interactions. Finally, the low trapping forces of the optical tweezer 20′ are a disadvantage. Two cells 1, 2 can no longer be separated from one another without problems with the optical tweezer 20′ after the mutual contacting and formation of intermolecular interactions.
A further generic technique for carrying out the above-named concept is described in WO 2005/083057. In this technique the cell to be examined is arranged on a magnetic carrier that can be shifted under the action of a magnetic field on the bottom of a conduit filled with liquid. A further cell that is to be made to interact with the first cell can be arranged on a further magnetic carrier that is shiftably arranged especially on a cover element of the conduit opposite the bottom. The cells can be made to interact with one another by a suitable alignment of the magnetic carriers. Even the technique described in WO 2005/083057 has the disadvantage that only individual cell-cell interactions can be examined. The geometric extension of the magnetic carriers prevents several cells from being brought in contact independently of each other with a cell to be examined. A further disadvantage consists in that only one-sided cell contacts are possible. The cell surface available for the examination is greatly limited by the depositing on the magnetic carrier. Finally, a disadvantage consists in that only global cell-cell interactions can be examined. The cell contact can not be limited to certain parts of the cell surface when using the magnetic carriers.
Thus, the previous techniques for carrying out the above-mentioned concept for in-vitro examinations are limited to special applications (e.g. examinations on planar surfaces, one-sided cell treatment). A tool for the handling of biological cells that is related to solutions and surfaces and that makes possible precise and reliable tests even for complex combinations of signal factors has, however, not been available yet.
The invention has the objective of providing an improved conditioning device for handling biological cells, in particular for purposes of testing, manipulation or examination, with which the disadvantages and limitations of the conventional techniques are avoided. The objective of the invention is furthermore to provide an improved conditioning method that is suitable for an in-vitro conditioning of biological cells.
These objectives are solved by a conditioning device and a conditioning method of the invention.